June 15, 1844 – Charles Goodyear and Vulcanized Rubber

On this day in engineering history, Charles Spencer Goodyear received U.S. Patent No. 3633 for vulcanization, a rubber-curing process named after Vulcan, the Roman god of fire. While working at a factory in Woburn, Massachusetts, Goodyear combined natural rubber and sulphur over an open flame. Although most of the mixture burned, the edges were perfectly cured. In his subsequent patent application, Charles Goodyear described how the addition of sulphur and "the action of heat at a regulated temperature" could be used to produce "India-rubber fabrics" that would not "become softened by the action of the solar ray or of artificial heat." Vulcanized rubber could also resist "oils at common temperatures" and withstand "exposure to cold".

Vulcanized Rubber and the Industrial Revolution

Goodyear's use of sulphur to cross-link polymer molecules revolutionized the rubber industry, but failed to make him a wealthy man. The Goodyear Tire & Rubber Company bears the inventor's name, but was founded nearly 40 years after Charles Goodyear died penniless. Although Goodyear didn't live long enough to travel in an automobile with vulcanized rubber tires, his journey aided industry in the nineteenth century. Before Goodyear's discovery, factories used leather soaked in oil to seal the small gaps between moving parts. This loosely-packed leather worked well enough at low pressures, but was unable to prevent the loss of high-pressure steam. Packing extra leather between pistons and cylinders helped, but introduced extra friction.

The Rubber People

Charles Goodyear may have been the first U.S. citizen to discover vulcanization, but he was not the first resident of the New World to cure rubber. In "Prehistoric Polymers: Rubber Processing in Ancient Mesoamerica," a 1999 study in Science magazine, researchers from the Massachusetts Institute of Technology (MIT) described how the ancient Olmecs harvested latex from the Castilla elastica rubber tree and mixed it with the sulphur-rich juices of lpomoe alba, a night-blooming vine. By processing rubber in this way, the Olmecs produced bouncing balls for a ritualistic sport that spread across Mesoamerica. Fittingly, the Aztecs called the Gulf Coast inventors of this game the Olmeca, a word meaning "the rubber people".